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Largely Improved Battery Performance Using Micro-Sized Silicon Skeleton Caged By Polypyrrole As Anode.

Research paper by Yingying Y Lv, Mingwei M Shang, Xi X Chen, Parisa Shabani PS Nezhad, Junjie J Niu

Indexed on: 03 Nov '20Published on: 07 Sep '19Published in: ACS Nano



Abstract

Various architectures with nano-structured silicon have demonstrated promising battery performance while posing a challenge in industrial production. The current ratio of silicon in graphite as anode is less than 5 wt%, which greatly limits the battery energy density. In this article, we report a scalable synthesis of large silicon cage composite (micrometers) that is composed of a silicon skeleton and an ultra-thin (<5 nm) mesoporous polypyrrole (PPy) skin via a facile wet-chemical method. The industry available, micro-sized AlSi alloy was used as precursor. The hollow skeleton configuration provides sufficient spaces to accommodate the drastic volume expansion/shrinkage upon charging/discharging while the conductive polymer serves as a protective layer and fast channel for Li+/e- transport. The battery with the micro-silicon (μ-Si) cage as anode displays an excellent capacity retention upon long cycling at high charge/discharge rates and high material loadings. At 0.2 C, the specific capacity of ~1660 mAh/g with Coulombic efficiency (CE) of ~99.8% and 99.4 % were achieved after 500 cycles at 3 mg/cm2 loading and 400 cycles at 4.4 mg/cm2 loading, respectively. At 1.0 C, a capacity as high as 1149 mAh/g was remained after 500 cycles with such high loading. The areal capacity of as high as 6.4 mAh/cm2 with 4.4 mg/cm2 loading was obtained, which ensures a high battery energy density in powering large devices such as electric vehicles.